From Chemical Topology to Molecular Machines
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00:00
Methyl iodideNobeliumChemistryUreaFoodOrganisches MolekülNobelium
00:24
ChemistryNobeliumNational Rifle AssociationMoleculeLactitolMachinabilityLecture/Conference
00:55
MoleculeFullereneChemistryChemical bondChemical propertyButcherChemistCandyAgricultureStorage tankMoleculeLecture/Conference
01:36
MoleculeFullereneChemistryChemical bondIsomerChemical compoundSpeciesBiomolecular structureChemistWine tasting descriptorsChemical bondMoleculeAtomic numberChemical structureLactitolChemical propertyKnotPlant breedingLot <Werkstoff>Germanic peoplesPhysical chemistryAnomalie <Medizin>ColourantArzneimitteldosisMan pageChain (unit)Lecture/Conference
06:11
NobeliumChemical compoundChemistryCatenanePhotochemistryMoleculeWaterSpaltflächeSample (material)ElectronElektronentransferLigandRutheniumCopperMultiprotein complexPascal (unit)LigandPhenyl groupBiosynthesisKnotChain (unit)CatenaneRutheniumMoleculeMetalWaterElectronChemical reactionCopperSpeciesTransition metalMultiprotein complexPhotochemistryChemistFunctional groupSetzen <Verfahrenstechnik>WalkingPhysical chemistryCoordination complexChemistrySpawn (biology)KetaminDetection limitBET theoryArzneimitteldosisKlinische ChemieChemical propertyLecture/Conference
12:01
NobeliumMeatCatenaneCopperBiosynthesisKnotMoleculeTetraederstrukturPascal (unit)Transition metalMetalLigandDelicatessenChemical reactionMotion (physics)VitalismRotaxaneMoleculeCopperSpeciesCheminformaticsElectronic cigaretteX-ray crystallographyCHARGE syndromeKinesinMachinabilityChemical propertyÜbergangszustandChemical elementAtomic numberProcess (computing)TetraederstrukturStickstoffatomMicrotubuleSystemic therapyChemical compoundProteinAzo couplingErdrutschChemical structureCell (biology)NobeliumWalkingSynthaseFrench friesIon channelChemistMedicalizationBarrel (unit)Spawn (biology)Sense DistrictMultiprotein complexMetamorphes GesteinDiethanolamineBiosynthesisAgricultureGas cylinderAtomKatalaseMeeting/InterviewComputer animation
20:08
CatenaneRotaxaneMotion (physics)CultivatorOptische AktivitätMachinabilitySystemic therapyAtomic numberStickstoffatomCatenaneCopperFunctional groupMultiprotein complexMoleculeController (control theory)Azo couplingGap junctionPreservativeHomeopathyLecture/Conference
21:48
CultivatorOptische AktivitätColumbia RecordsMoleculeSpeciesCopperMoleculeSystemic therapyElectronAtomic numberProcess (computing)ThermoformingMultiprotein complexBattery (electricity)Chemical reactionAzo couplingLighterStickstoffatomMotion (physics)Omega-6-FettsäurenFatigue (medical)Lecture/Conference
24:07
MoleculeNobeliumMyosinSystemic therapyMetalChemical propertyMoleculeFunctional groupChemistSpring (hydrology)CheminformaticsStream gaugeLactitolFilm grainCell (biology)Lecture/Conference
25:52
NobeliumMagmaMyosinHeterodimereMoleculeSpeciesMotion (physics)MetalTransition metalCatenaneStream gaugeChemical compoundRotaxaneAlpha-1-RezeptorMeatPascal (unit)Tumorassoziierter TrypsininhibitorPill (pharmacy)KnotMultiprotein complexFraser syndromeChemistrySpeciesMachinabilityMoleculeThermoformingFrench friesSystemic therapyElectrochemistryProcess (computing)Organisches MolekülChemical propertyChemistTuberculosisMetallorganische ChemieChemische SyntheseMotion (physics)ÜbergangszustandElongation (astronomy)Left-wing politicsSteelCultivatorBiosynthesisFilm grainFalconryPainBiologische LandwirtschaftChemistryPerm (hairstyle)Cell (biology)Electronic cigaretteTrauma (medicine)MedicalizationLecture/Conference
30:52
NobeliumFunctional groupColumbia RecordsPentose phosphate pathwayStress (mechanics)ErdrutschKreide <Gestein>Lecture/Conference
31:29
Mill (grinding)NobeliumFunctional groupColumbia Records
Transcript: English(auto-generated)
00:14
Well, I'm very happy to be part of this beautiful Lin Dao meeting and I would like to thank
00:22
the organizers of this beautiful meeting. I also would like to thank the Nobel Foundation as well as Madame La Contesse Bernadotte for her interest in science and for promoting science which is nowadays very important. So we'll talk about topology and molecular
00:49
machines and I will start with a bit of topology, very, very simple notions, notions which real topologists would consider as totally trivial. So if you define topology, this is the science
01:10
of infinitely deformable objects, so you can distort the objects as much as you like and provided you do not break anything, you do not modify the properties, the topological
01:25
properties of the object. In chemical topology now, you can consider bone lengths and angles but again you can pull on the bones, you can contract the bones,
01:42
you can distort the angles, the topological properties of the molecule are not going to be modified. Now if you look at a very classical molecule and I'm sure that even non-chemists, people in the audience have heard of C60. So C60, it's like a soccer
02:09
ball, I think there is another, yeah this is better. C60 is like a soccer ball, so
02:23
it's a three-dimensional species, you can even rotate it and C60 can be drawn in such a way that it's graph, the way you draw it is planar and this is called Schlegel
02:41
diagram, so you have 60 points here, 60 vertices and this is planar because you can draw it in a plane without crossing points, which makes it topologically trivial, so
03:00
topologists would not consider that this is a very exciting species. Interestingly, if you look at basically all the molecules which have been made or all the natural substances which have been isolated and characterised, these species are topologically trivial,
03:22
they have a planar graph, you can draw them in a plane without crossings and so again they are not very interesting from a topology viewpoint. Now let's look at how a chemist became interested in topology and there was a historical paper published in 1961
03:49
on chemical topology, so that was simply the title of the publication published in the Journal of the American Chemical Society and in this paper the two authors
04:04
Fresh and Wasserman explain that topology can also be considered in the molecular sciences. Just an example, you take a ring here, so this is of course trivial because you can
04:21
draw it in a plane without crossings, so it is topologically of no interest, but you can take exactly the same sequence of atoms and chemical bonds and dispose the ring in a totally different fashion so as to obtain a knotted species. Here you have the trifle knot and
04:44
this trifle knot cannot be represented in a plane without at least three crossing points. So this is of course a non-planar graph and it is topologically of interest. So these knotted structures were known in topology, in mathematical topology
05:05
for decades and decades but in a way chemists ignored them completely till this publication. Another very important example is that of two interlocking rings which can again contain
05:24
exactly the same sequence of atoms and chemical bonds as the two separate rings, but those two species, the interlocking rings and the two separate rings have different topological properties and they are also expected to have different chemical and physical
05:44
properties. So now let's look at how it started. So there was a very important contribution from German chemists, Lüttinghaus, Professor Lüttinghaus and Professor Schild working at the
06:08
Hamburg by the way and these people were very much interested in topology and they made what they called a catenane from the Latin word catena which means chain and a catenane is the
06:25
simplest, the smallest chain you can think of made out of molecules or made out of rings. So they made such a species and they published the work in 1964. So it was beautiful work,
06:41
very very elegant but exceedingly difficult and also very difficult to reproduce because there were 22 individual chemical steps between the starting molecule and the final target, the catenane. So everybody greeted the work but it was so difficult to make catenanes
07:08
that the people gradually lost interest in the field of catenane for catenanes and so we had to wait for some time and I will now explain to you why we became interested in
07:25
catenane and what was our strategy. So when I started my group many years ago at the very beginning of the 80s, I was an inorganic photochemist. I was working in the field of inorganic photochemistry with my group and there was a grand project at the time which was to be
07:50
able to cleave the water molecule to H2NO2, kind of a dream reaction and it is still a dream reaction because it still doesn't work very efficiently. And again
08:06
in the 70s and in the 80s there was a transition metal complex, a molecule of this type here, which was very very popular and used by many groups interested in splitting the water molecule.
08:24
So this is a ruthenium complex, it's a nice octahedral complex, it has a very nice color, of course it has to be a colorful molecule because it will absorb the the photons from solar light and its excited state had lots of interesting properties,
08:46
ability to transfer an electron or electronic energy, so this molecule was and still is one of the most popular molecules in the field of water splitting. But there is a small problem
09:02
here, ruthenium is very expensive, it's a novel metal and of course it would be much better to use a very cheap metal, a first row transition metal. And so we decided to switch from ruthenium to copper and that decision was also triggered by the visit
09:29
of Professor David McMillan from Purdue University who was an expert in the field of copper photochemistry. So David McMillan was on sabbatical leave in Strasbourg,
09:45
he was formerly a professor in Jean-Marie Leszt, but we also had a lot of interaction, in fact he worked also very much with us and at the time we had made a very simple molecule like this one,
10:04
a question shaped molecule which was new, very surprisingly nobody had made this molecule before us and when David saw this molecule he said well we must collaborate, you will make the copper complex and we will do all the photochemistry and all the photophysics
10:26
studies and this is exactly how we started. So we made this copper complex, a very simple copper complex starting from two such molecules to question shaped molecules and we obtained this
10:45
quantitatively and there were lots of photochemical and photophysics studies done in Purdue and so that was it. But, and now the but is very important, if you look carefully at this
11:00
molecule you can conceive, you can realize that you link this point to this other point and this point to this other point here you obtain something of interest. You make a ring here, you make another ring here and those two rings are going to be
11:24
interlocking, so I will do it with my hands. You have your copper here let's say, you do this and then you will cyclize and make a cationane, that was very simple and at that stage
11:40
we had to decide whether we would go on in the field of inorganic photochemistry or be more adventurous and jump in a field which we didn't know so well and of course the conclusion is that we decided to jump. At the same time a very good friend
12:02
decided to join my group, so we knew each other for many many years, we were even students together and she has all the expertise required for making complicated organic molecules. So this is Christian Ditrech-Wiecheke and we started on the project trying to make a cationane
12:27
using copper as an assembling element, orienting element and it worked. So we started the project in October 1982 and very surprisingly in October
12:45
1983 we had our first paper, so she was so efficient that everything worked beautifully and we had our first paper published in Tetrahedron Letters which is not a high-impact journal,
13:02
you know nowadays I think all young scientists want to publish in high-impact journals, I'm not sure it is really indispensable and even more we published in French, well that was more for fun you know, we knew it was novel and we thought well let's try to
13:25
publish in French and I probably have one percent of my publications in French and this paper belongs to this one percent and it says I'm not going to insult you and translate it to English, I'm sure there is no need. Now let's look at the strategy, it is very much related
13:47
to what I just said and you start from a transition metal, you mix with two organic fragments which are half a circles or question shaped, you obtain this intertwined or entwined species
14:05
and now you cyclise here, you make a ring here, you make another ring here and at the end of the day you have your catalain, very very simple. Now let's look at the molecules,
14:21
just to remind you you know that was published in 83, 84 and we had basically no computers in our laboratories and chemdo didn't exist, can you imagine you the young people a world without chemdo and it was a world without chemdo you know, it was the pre-chemdo era
14:46
and so we had to draw the molecules and in fact I was in charge of that, so I was drawing the molecules, Christiane Ditre-Buchequet was making the molecules, her part was much more
15:03
important than mine but finally it was a very nice collaboration. So as I said we obtained this molecule, then we made a ring here, made another ring here, we obtained the catalain
15:21
and that was a three-step synthesis, very very straightforward from commercially available molecules financially, three steps and we could make in let's say two or three weeks one gram of such a compound. So the situation was very significantly improved
15:43
as far as catenains were concerned, these molecules appear to be accessible, all of a sudden they became very normal molecules. I have a small animation made by a student of mine recently, just for those who had difficulties with my drawings,
16:07
so we start from the question shaped molecules, we make the entwined species and now we make a ring on one side, another ring on the other side and we have the catenain.
16:21
There is another strategy which is to start from a pre-synthetized ring with a coordinating fragment, two nitrogen atoms here, now we will mix with copper, the second fragment will thread inside the ring and you cyclize so as to obtain the same catenain.
16:45
So we have two strategies, we could of course isolate everything, characterize everything and so this is the copper complexed catenain, we have an x-ray structure
17:02
which shows that it's a very compact structure. Here we have the demetallated species with a totally different structure, totally different shape, the two rings can freely glide within one another, the process is reversible and so we are not really
17:23
in the field of molecular machines but at least we are on the way because the system undergoes a complete metamorphosis, this is the way we called the process. For many years we have been interested in new topologies and I should say that we devoted probably more time, more effort
17:47
to making and studying new topologies than to molecular machines and here are just a couple of examples, probably the most difficult but to us at least the most attractive one
18:03
was the making of a trifle knot, the same species as the one I discussed at the very beginning of my lecture and something also very challenging was the solomon link which we could make in 1994 and then we spent a couple of years
18:23
studying, improving the procedures and looking at the properties. Now let's switch to switches and machines, so I was very happy to meet yesterday with Professor Walker, Sir Walker
18:44
who was a Nobel laureate some time ago in the field of ATPase, ATP synthase but this slide is just to remind you that molecular motors and molecular machines are essential in biology, you cannot think of any important biological process not involving
19:08
motor proteins which are simply molecular machines or molecular motors. There is another example here which is also extremely important, the kinesin
19:24
working on a microtubule in the cell and carrying molecules within the cell but there are many many examples which of course we have no time to discuss. Let's go back to catenase and retaxanes, retaxanes are simply species of this type,
19:46
a ring has been threaded by an axis and at both ends of the axis the people could attach big stoppers so as to prevent unthreading, so you can easily figure
20:01
out that if you can move a ring from this position to that position you are very close to making a linear motor like a piston and a cylinder and if you can rotate a ring here about this axis you are on the way to rotary motors, the same here,
20:23
let's say on the way towards rotary motors and I would just like to spend two minutes on the very first molecular machine we made in our group. It's a catenane and we will do something similar to what is represented here. It's not a real rotary motor because we have
20:47
no control over directionality and if you want to look at real rotary motors you have to be patient, I mean historically, and wait till 1999 when the group of Ben Ferenga published
21:03
their beautiful work, the first rotary motor made out of molecules. So we start from here and we have a copper one complex and this copper one complex is very stable because
21:23
copper one likes to be coordinated to four nitrogen atoms, so here copper one which is reduced state of copper is surrounded by four nitrogen atoms disposed as a tetrahedron,
21:42
so everything is very stable. Now we will send a perturbation to the system and the perturbation is just oxidizing copper one to copper two. We generate a new species copper two plus but this species is very unstable because copper two plus wants to be five coordinate or six
22:05
coordinate which means that it likes to have five or six nitrogen atoms in its surrounding. So what will go on? The three nitrogen atoms which were here at the beginning doing nothing
22:21
will start to move. This fragment will kick out this other fragment so as to replace it in the vicinity of the copper and now you have a five coordinate copper, so one, two, three, five nitrogen atoms around copper, copper two plus and copper two plus is now very very
22:45
happy and it forms a very stable complex. You can go back, reduce copper two to copper one, you generate again a very unstable species which will relax by moving the ring here so as to regenerate the starting form of the molecule. I have a small video which has basically no
23:08
scientific value except that it may help visualize the process. So here we have copper one, four nitrogen atoms here and you see that there are three nitrogen atoms waiting for
23:23
better times, let's say, doing nothing. Now we abstract an electron, we generate copper two, the system will immediately rearrange and you obtain a very stable copper two complex. You can re-inject an electron, you will do the opposite motion, etc.
23:44
And I think the beauty of this system is that there is strictly no fatigue. You can do it as many times as you like. It's a very simple chemical reaction which is just oxidizing copper one or reusing copper two, so nothing bad can happen. At the same time, exactly at the same time,
24:09
Bicel Córdova, Angel Kiefer at the University of Miami and Fraser Stoddart, still in the UK at the time, published a very nice paper on the making and the properties
24:25
of a molecular shuttle, the simplest molecular shuttle being represented here. A ring can glide from a green station to a red station and of course it can go back to the green station.
24:42
So I think that was a very important piece of work also because it triggered interest for a new field which you can call molecular computing which simply means storing information, processing information using molecules. But of course we have no time to discuss about that.
25:07
I would like to finish up with a system which we liked, which was made in our group but again I will skip all the chemical parts, all the chemical details, but we wanted to make
25:24
an artificial muscle, a molecule behaving reminiscent of natural muscles. You probably know that muscles mostly consist of filaments and they are very very different
25:44
from springs, from metal springs in which you have tension. Here you have no tension, simply the filaments will glide along one another and the thin filaments, actin, namely actin, will glide towards the center of this elementary muscle which is called a sarcomere
26:07
which in a way leads to contraction of these species so it will move to the right, this part will move to the left. It's an ATP consuming process so it requires energy
26:21
and now the muscle is contracted and when it relaxes the process doesn't consume any energy and you go back to the elongated or relaxed form of the muscle. So we decided to make a molecule of this type, I mean in terms of synthesis it is relatively complex,
26:45
so we have a ring here, a deep blue ring which is attached to a deep blue filament. The deep blue filament is threaded through a pale blue ring which is also attached to
27:00
another filament threaded inside the deep blue ring so we made such a molecule, we characterized it completely and we could trigger this process contraction from 8 nanometers to 5.5 nanometers and elongation back to the 8 nanometers in length and we could do that using a chemical signal
27:29
but as I said we have no time to discuss all this. Let me now conclude, I think before the emergence of molecular motors and molecular machines, chemists were used
27:44
to look at their molecules as relatively motionless steel objects, of course undergoing motion, vibrations, stochastic movements but they were very far away from let's say molecular
28:02
motors and molecular machines like rotary motors, Fahrenheit systems or muscles or shuttles and I think this in connection to biology probably had some echo among chemists or
28:25
molecular chemists and biologists. Transition methods played a very important role because they allowed us to make the molecules by attracting various organic fragments,
28:40
gathering them, dispersing them in a very well defined geometry and thus allowing the preparation of the target molecules and they also provided these molecules with photochemical or electrochemicals or even chemical properties which allowed us to set the molecules in motion.
29:05
I know we have limited time but I just would like to say that what I just spoke about is a teamwork. The team is very important especially in synthetic chemistry and the beauty of the
29:20
French system is that you can work with permanent people and these permanent people can be extremely efficient when they are associated to PhD students, to postdocs and so of course there is a long list of people here, we have no time to name them but I owe them a lot
29:46
and I would like to thank them. Finally let me thank my university, Strasbourg University, the French CNRS and various institutions, Northwestern University where I spent three years
30:03
part-time after the CNRS politely suggested me to retire, my good friend Jean-Marie, also a good friend Malcolm Green with whom I learned a lot of organometallic chemistry and
30:22
inorganic chemistry, two teachers, Uri Saint and Weiss who had a huge impact on my interest for molecular sciences, my family of course and my two friends Fraser Stoddart and Ben Ferenga and if I still have one minute or so I'd like to add a few remarks for the younger people.
30:48
Believe me, novelty is the most important. When you decide at some stage to start your own chemistry, your own science, novelty is number one. Another point which I'd like to stress
31:03
is that interaction is also extremely important either within your surrounding, your neighborhood or even outside and don't be scared to jump from a field in which you feel very comfortable, very warm to another field which you don't know so well. This is how you can perhaps
31:26
discover new things and be confident. I think there was already a slide by Dick Schrock about being confident, being self-confident. Do not ask yourself whether you are good enough to
31:42
start in a new field, just do it. Thank you very much.